Elastic recovery performance and buckling pressure retention of spring clips
- What factors affect the elastic recovery performance of the spring bar?
The elastic modulus of the material is the core factor. Materials with high elastic modulus are easier to recover after deformation. For example, spring bars made of high-quality spring steel have better elastic recovery performance. The heat treatment process directly affects the internal structure of the spring bar. Insufficient quenching will lead to low hardness and poor elasticity; excessive tempering will reduce elasticity. Reasonable heat treatment can enhance its elastic recovery ability. The structural design of the spring bar is also very important. The structure with uniform cross-section and smooth transition can reduce stress concentration and is easier to recover after deformation, while the complex structure may affect elastic recovery due to excessive local deformation. Fatigue damage during use will gradually weaken the elasticity, and long-term alternating loads will cause microcracks inside the material, resulting in a decrease in elastic recovery performance. Environmental factors such as high temperature will soften the material and low temperature will increase brittleness, which will reduce the elastic recovery ability of the spring bar.
- What effect does the size of the buckle pressure have on the fixing effect of the rail?
Excessive buckle pressure may cause plastic deformation at the bottom of the rail, affecting the service life of the rail. At the same time, the spring bar is in a high stress state for a long time, prone to fatigue fracture, and reduce the fastening reliability. If the buckling pressure is insufficient, the rails cannot be effectively restrained. When the train is running, the rails are prone to longitudinal or lateral displacement, resulting in changes in the track gauge and threatening driving safety. Appropriate buckling pressure can make the rails fit tightly with the sleepers, ensure uniform load transmission, reduce vibration and noise, and improve the smoothness of train travel. Uneven buckling pressure will cause unbalanced force on the rails, local stress concentration, which may cause rail cracks and accelerate the wear of spring clips and other fasteners. The buckling pressure needs to match the line conditions. Heavy-load lines require greater buckling pressure to resist the load, and high-speed lines need to balance buckling pressure and elasticity to avoid excessive constraint of the rails.
- How to detect the elastic recovery performance of spring clips?
Use the loading-unloading test, apply a specified deformation to the spring clip and then unload it, and measure the residual deformation after recovery. The smaller the residual deformation, the better the elastic recovery performance. Generally, the residual deformation is required not to exceed 0.5mm. The fatigue testing machine simulates the alternating load, and after a specified number of cycles, the elastic parameter changes of the spring clip are detected. If the parameter attenuation rate is less than 10%, the elastic recovery performance is considered qualified. Using stress-strain curve analysis, in the tensile or bending test, record the stress-strain relationship of the spring clip. The spring clip with a stable slope in the elastic stage and a curve near the origin after unloading has excellent elastic recovery performance. Test the elastic recovery ability of the spring clip at different temperatures, and conduct tests in the range of -40℃ to 60℃ to ensure that it can still maintain good elasticity at extreme temperatures. Sample and test the spring clips in use, compare the elastic indicators of the new spring clips, evaluate the degree of performance attenuation, and provide a basis for replacement.
- How will the buckle pressure of the spring clip change in long-term use?
In the initial use, the buckle pressure of the spring clip will naturally decay by 5%-10% due to plastic deformation and stress relaxation of the material, and then tend to stabilize. Long-term vibration causes the contact parts of the spring clip with the rail and sleeper to wear, resulting in a decrease in effective deformation and a gradual decrease in buckle pressure. This attenuation is more obvious in the curve section. Environmental corrosion will weaken the elasticity of the spring clip, especially in humid or dusty areas, where rust reduces the cross-section of the spring clip, reduces elasticity, and reduces buckle pressure accordingly. Repeated temperature changes will aggravate the fatigue damage of the spring bar, reduce its elastic modulus, and make it unable to maintain the original buckle pressure. This change is more prominent in areas with large temperature differences between the four seasons. Improper maintenance such as over-tightening or frequent disassembly will destroy the elastic structure of the spring bar, resulting in abnormal changes in buckle pressure and shortening its effective service life.
- How to improve the buckle pressure retention capacity of the spring bar?
Select high-strength spring steel such as 60Si2MnA, and optimize the heat treatment process to improve the material's fatigue resistance and relaxation resistance, and enhance the buckle pressure stability. Improve the design of the spring bar structure, adopt an arc or variable cross-section structure, make the stress distribution more uniform, and reduce local fatigue. For example, the SKL12 spring bar improves the buckle pressure retention capacity through structural optimization. Strictly control the manufacturing accuracy to ensure that the size of the spring bar meets the design requirements, avoid uneven buckle pressure due to size deviation, and affect the long-term retention effect. Regularly apply oil to the spring bar for rust prevention, and use galvanizing or anti-corrosion coating in coastal or industrial areas to reduce the impact of corrosion on elasticity. Establish a reasonable replacement cycle and replace the spring clips in time according to the pressure attenuation law before the pressure drops to 80% of the standard value to ensure the track tightening effect.